U.S. Pat. Nos. 4,589,441, 4,708,084, and 5,236,175 are hereby incorporated by reference into this disclosure.
The present invention relates to systems and valves for controlling the flow of water between a reservoir, such as a livewell on a fishing boat, and a water source, such as a lake or river. More specifically, the invention relates to an improvement in the material of which such valves are made.
The water distribution and valve systems disclosed in U.S. Pat. Nos. 4,589,441, 4,708,084, and 5,236,175 represent typical prior art apparatus for controlling the flow of water into and out of fishing boat baitwells and livewells. Water is drawn through a flow control valve by a pump which then directs water flow to the livewell inlet. These patents disclose various valve arrangements and functions which provide enhanced operator control during livewell filling, recirculation and draining. The disclosure of U.S. Pat. Nos. 4,589,441, 4,708,084 and 5,236,175 are incorporated herein by reference.
Systems and valves made in accordance with these patents are widely used by many manufacturers of sport fishing boats. For example, most bass fishing boats built today incorporate a livewell system manufactured under one or more of these patents. While these systems and valves have performed well, the eventual deterioration of the valve seal material used in the control valve has been a recurring problem.
A thermoplastic elastomer used for the valve seal has provided a desirable combination of properties which has met the known operating conditions and performance requirements of the system and valves. The chemical resistance of the thermoplastic elastomer material was, according to known specifications, suitable for the application. While most systems have performed reliably for many years, as the number of boats using this type of system have increased, so have the number of valve seal material failures. The eventual failure of elastomeric seals is generally expected and tolerated by boat owners as a maintenance item. The repair of the valves, however, is difficult due to the generally inaccessible location of the valve in the boat bilge. Thus eliminating this problem has become important to both boat manufacturers and dealers.
The failure of the valve seals was studied in an effort to determine the cause of the problem. Many possible chemical contaminants were evaluated. Mold release agents used in the manufacture of fiberglass and plastic livewell tanks, and antifreeze used to flush out the livewell to winterize the boat were considered but were not found to be the problem. Herbicides and insecticides used in treating lakes and waterways and livewell additives such as tranquilizers used to calm fish were also not found to be a factor. Samples of the failed valve seals were examined and the characteristics of the failures (hardening and shrinking) were typical of heat aging failures. But while temperatures in the bilge of the boat can exceed over 100.degree. F. for extended periods, the valve seal failures occurred in cooler northern climates as well as in hotter southern locales.
Only after examination of the potential causes for the valve seal failures over several years was the cause finally identified. One model valve, using the same valve seal material as the other valves, had no failure. This valve, however, was used only to drain the livewell. No outside water was drawn through it. Thus, something in the outside water was thought to cause the failures. Initial speculation was that engine exhaust gases or gasoline fumes, concentrated in the low pressure area behind the boat, were being drawn into the livewell system along with the water.
Tests conducted upon the valve seal material that was conventionally used with these valve systems (a thermoplastic elastomer) showed that the material was undergoing a slight swelling followed by a substantial shrinkage and hardening of the material. This swelling/shrinkage phenomenon mimicked the actual failures of the valve seals in the field. Further testing revealed that gasoline was leaching out the plasticizer in the elastomer, causing dramatic failure. In other words, a relatively low concentration of gasoline fumes, over time, was in fact causing the seal to gradually deteriorate.
Materials resistant to exposure to gasoline were considered as replacements for the seal material. However, the material also needed to possess desired attributes of flexibility and ease of manufacture. O-rings are commonly made from nitrile and used in marine valves, as it is typically stocked by suppliers for this application. However, thermoplastic elastomers have conventionally been employed as the valve seal or "flapper" material because they permit lower cost tooling and provide easier design configuration changes, while also being processed cheaper than thermoset materials such as nitrile.
Thermoset synthetic rubbers were then identified as the most desirable materials for fabricating the valve seals/flappers. These include nitrile and flouropolymer thermosetting resins, with nitrile being the preferred choice as it can be readily and economically molded. The use of nitrile as the valve seal material has eliminated the field failures previously encountered. With no material failures, the reliability, longevity, and customer satisfaction of the livewell/baitwell systems employing these valves has been enhanced.